Thunderbird cathedral hull transom and stringers

tbird175

Petty Officer 1st Class
Joined
Sep 15, 2008
Messages
253
I have been exploring the extent of the rot in my 17' thunderbird (Seminole outboard) today. The transom has rot across the whole bottom half. I pulled some the fiberglass off from the inside to expose part of the damage. The ends of 2 of the the 3 stringers are deterioated for less than a foot from their connection with the transom. These stringers form the sides of the sump. The center stringer which stops short of the transom (connects to the sump) and the remainder of the other 2 stringers are in good shape. There is some rot in the deck (plywood) where the fiberglass deck covering had cracked allowed water to penetrate.

My questions are:
1. Is it possible to splice the two deterioated stringers to remove the deteriorated section (scab with suitable material and then glass over)?
2. If it is feasible to splice the two stringers would it be okay to cut the cap about 2' from the transom and only remove the rear portion of the cap to replace the transom? This would be a lot simpler. The cap is going to be very heavy and difficult to handle. The bow area is part of the cap (deck and seating).

If I have to replace all of the 2 deterioated stringers I will have to remove the entire cap. If I do this I will replace all of the deck. Any advice will be appreciated. This will be my first boat hull repair and I am sure that I will be asking a lot of questions. I am experienced at wood working and structural design, but I am not familiar with boat construction.
 

HopeSheFloats

Lieutenant Commander
Joined
Jun 12, 2009
Messages
1,674
Re: Thunderbird cathedral hull transom and stringers

I'm not qualified to answer, but will say that 'simpler' equates {in my book anyways} to 'band-aid'...Heard of others splicing, but imo if you plan on keeping her for more than a season or two, do it right and she'll probably out last you.

Just my thoughts, those with more experience will chime in I'm sure...best of luck either way ;)
 

archbuilder

Vice Admiral
Joined
Sep 12, 2009
Messages
5,697
Re: Thunderbird cathedral hull transom and stringers

I agree.....I think the more you get into it, the more damage you will find. Its not as difficult as it may sound, you just have to be persistent! This is the right place for advice and encouragement! Looking forward to seeing your progress!
 

tbird175

Petty Officer 1st Class
Joined
Sep 15, 2008
Messages
253
Re: Thunderbird cathedral hull transom and stringers

It is evident that the source of the rot in my transom and the ends of the stringers was from a poor seal around the outboard engine mounting bolts. The stringers are encased in fiberglass. The only deterioration is at the end that joins the transom. The soft spots in the deck were away from the stringers so ther was no stringer damage there. I will replace all the deck from the step up to the bow to the transom. It wil be difficult to replace the transon wood with the splash well in place.

I would like to cut the cap just forward of the transom rather than removing the entire cap (really no place to store it). I would like advice on this cut and the best way remove the damaged ends of the stringers and splice back to the remaining good portion.

Any advice will be appreciated.
 

rockyrude

Lieutenant Junior Grade
Joined
Sep 10, 2007
Messages
1,121
Re: Thunderbird cathedral hull transom and stringers

I'm in the middle of restoring an 18' apache, the stringers on mine were not totally cased by fiberglass and water had wicked its way up along the wood and fiberglass alot further that I had expected. I don't remember if yours is a bowrider, mine is and the deck goes all the way to the bow under the fiberglass walkway in the middle.
 

jonesg

Admiral
Joined
Feb 22, 2008
Messages
7,198
Re: Thunderbird cathedral hull transom and stringers

It can be done, had a shipwright show me how to do mine without being too invasive.

Cut the splashwell off and glass it back when done with repairs, make your cuts so they are not too visible , cut along seams etc. Make sure you get access to the whole transom rear face. About 3 feet will allow room to stand, you can leave the cap on.

Splicing , in for a dime , in for a dollar.
Suppose it depends if you plan on keeping it.
Its a shame to do the transom only to sell it.
If you do the transom it makes sense to do stringers.
I left the cap on mine, I cut around the perimeter of the deck.
 

tbird175

Petty Officer 1st Class
Joined
Sep 15, 2008
Messages
253
Re: Thunderbird cathedral hull transom and stringers

I'm in the middle of restoring an 18' apache, the stringers on mine were not totally cased by fiberglass and water had wicked its way up along the wood and fiberglass alot further that I had expected. I don't remember if yours is a bowrider, mine is and the deck goes all the way to the bow under the fiberglass walkway in the middle.

Yes my Seminole deck also goes to the bow, the bow rider section (deck and seating) is part of the cap. My stringers are completely encapsulated with glass.
My plan is to cut into the stringers away from the rot to determine the extent of the damage. If it is less than a few feet I prefer to remove the damaged area and splice into the good portion. The only way that I can replace the entire stringer is to remove the entire cap.
 

tbird175

Petty Officer 1st Class
Joined
Sep 15, 2008
Messages
253
Re: Thunderbird cathedral hull transom and stringers

It can be done, had a shipwright show me how to do mine without being too invasive.

Cut the splashwell off and glass it back when done with repairs, make your cuts so they are not too visible , cut along seams etc. Make sure you get access to the whole transom rear face. About 3 feet will allow room to stand, you can leave the cap on.

Splicing , in for a dime , in for a dollar.
Suppose it depends if you plan on keeping it.
Its a shame to do the transom only to sell it.
If you do the transom it makes sense to do stringers.
I left the cap on mine, I cut around the perimeter of the deck.

I plan to keep the boat after the repairs. I cannot fully replace the stringers without removing the cap because the deck extends to the bow under the bow rider section like rockyrudes's.
 

tschmidty

Chief Petty Officer
Joined
Mar 24, 2010
Messages
462
Re: Thunderbird cathedral hull transom and stringers

Really it comes down to your judgement on what you are comfortable with. Are you planning on keeping it? What kind of waters are you going out on?

There is nothing entirely wrong with splicing/scabbing but it will never quite as strong as a whole piece. Sometimes that is OK. Honestly I'd be OK as long as I was planning on keeping it, I'd hate to sell it to someone like that. :)

This is a classic case of wanting someone to tell you what you already want to do, right?
 

tbird175

Petty Officer 1st Class
Joined
Sep 15, 2008
Messages
253
Re: Thunderbird cathedral hull transom and stringers

Really it comes down to your judgement on what you are comfortable with. Are you planning on keeping it? What kind of waters are you going out on?

There is nothing entirely wrong with splicing/scabbing but it will never quite as strong as a whole piece. Sometimes that is OK. Honestly I'd be OK as long as I was planning on keeping it, I'd hate to sell it to someone like that. :)

This is a classic case of wanting someone to tell you what you already want to do, right?

Yep - That is what I am hoping for.
 
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